Prior art parallel-type interfolders and accordian pleating apparatuses are known which comprise sufficient folding guides that all folds are positively made about a machine member. Such apparatuses having a fan-shape array of elongate guides are exemplified by U.S. Pat. No. 1,122,511 which issued Dec. 29, 1914 to Solomon Lazar; U.S. Pat. No. 3,038,718 which issued June 12, 1962 to Maurice M. Balsam; U.S. Pat. No. 3,784,186 which issued Jan. 8, 1974 to Robert Lenthall et al.; and U.S. Pat. No. 3,850,425 which issued Nov. 26, 1974 to Nicholas Marcalus et al. A parallel type interfolding apparatus comprising guides having saw-tooth shape apertures through or between machine members is exemplified by U.S. Pat. No. Re 12,204 which issued Mar. 15, 1904 to Edwin D. Casterline. U.S. Pat. No. 3,536,317 which issued Oct. 27, 1970 to Ronald J. Billett interfolds wide sheets from parent rolls and slits them into facial tissue or napkin widths after the sheets have been interfolded by being passed between longitudinally extending guides.
These and other known interfolders commonly have problems such as access to machine members and adjustments, maintaining sufficient visible contact with the material-in-process for assuring quality control, and sufficiently controlling the folding and bundle formation to continuously and reliably produce square-cornered bundles of unwrinkled product. However, none of the discovered prior art interfolding apparatuses has solved the problems associated with interfolding in the manner nor to the degree of the present invention. For instance, in interfolding apparatuses comprising oppositely disposed guides, some guide members must be opened or moved to initially thread the webs therebetween whereas apparatuses embodying the present invention have no such oppositely disposed folding guides. That is, all of the webs being interfolded in an apparatus embodying the present invention are drawn across the top of a fan-shape folding table; not between elongate members or through saw-tooth apertures. Moreover, the preferred embodiment of the present invention has, as is described fully hereinafter, slitters which make slits visible to the machine operators, adjustable guide rollers for maintaining bundle squareness, and other improvements with respect to prior art apparatuses.